1. Field of the Invention
This invention relates to ethylenically unsaturated isocyanurates and more particularly to ethylenically unsaturated isocyanurates having improved adhesion, and excellent retention of physical properties when exposed to high temperature for structural molding applications.
2. The Prior Art
U.S. Pat. No. 4,128,537 to Markiewitz and U.S. Pat. No. 4,195,146 to Markiewitz et al each discloses the preparation of ethylenically unsaturated isocyanurates in a two-step process wherein a polyisocyanate is first reacted with an ethylenically unsaturated monohydroxy alcohol in the presence of a copper salt to form an isocyanate-containing urethane. Thereafter, the urethane is trimerized in the presence of a suitable catalyst, such as a tertiary amine, to prepare the ethylenically unsaturated isocyanurate. Other patents of interest include:
U.S. Pat. No. 4,035,439 and U.S. Pat. No. 4,088,257 both to Stevenson disclose a one component low-shrink molding composition comprising a linear polyurethane thermoplastic in combination with a dicyclopentadiene modified thermosetting polyester resin and a coreactive vinyl monomer.
U.S. Pat. No. 4,777,209 to Hefner et al discloses compositions of polycycloalkenyl-terminated unsaturated polyesters and vinyl reactive plasticizers composed of vinyl terminated urethane oligomers containing at least one polyglycol unit.
The ethylenically unsaturated isocyanurates may be homopolymerized or copolymerized with ethylenically unsaturated monomers to form high molecular weight polymers having excellent physical properties. For example, the ethylenically unsaturated isocyanurates have been found to be particularly useful in applications such as castings, coatings and laminates where it is desirable to have excellent combinations of flexural, tensile and impact properties at elevated temperatures.
The ethylenically unsaturated isocyanurate resins have been considered for the formulation of molding compositions, referred to in the art as "sheet molding compounds" (SMC), which generally comprise a curable ethylenically unsaturated polyester resin as a major component dissolved in a suitable unsaturated cross-linking monomer containing terminal vinyl groups, such as styrene and admixed with curing agents, polymerization inhibitors, release agents, fibrous reinforcing materials, fillers, and pigments.
These SMC systems can be molded into articles having various forms by various molding processes, such as compression molding, transfer molding and injection molding under heat and pressure.
Although ethylenically unsaturated isocyanurates are known to the art, these compositions when considered for the formulation of SMC systems for structural automobile part applications lack the requisite adhesion properties for bonding these parts to each other or other parts used in the assembly of automobiles.
Therefore, the art is seeking means by which the adhesion properties of molded ethylenically unsaturated isocyanurate resins can be substantially improved so that these compositions may be more effectively used in the formulation of SMC systems for the manufacture of automobile parts.